1. Field of the Invention
The present invention relates to a three-dimensional display apparatus and a three dimensional display method for displaying a volume rendering image of a three-dimensional image composed of a plurality of tomographic images which have been obtained by tomographic imaging of an object, as well as a program for causing a computer to execute the three-dimensional image display method.
2. Description of the Related Art
In recent years, three-dimensional images of high quality are increasingly used for diagnostic imaging, accompanying advances in medical instruments (for example, multi-detector CT's, and the like). Further, analysis of such three-dimensional image facilitates grasping the three-dimensional shapes of various organs present in the interior of the body, and further enables the relative positional relationships among the respective tissues of arteries, veins, and tumors present in the organs and three-dimensional structures thereof to be understood. In such a case, a specific organ and a specific structure in the organ are extracted by using various image processing algorithms and a three-dimensional shape is projected onto a two-dimensional plane by display method such as volume rendering (VR) and the like so that the three-dimensional structure thereof can be understood.
Here, when the three-dimensional display is displayed by VR, an organ, a tissue, a structure, and the like of interest are extracted, and a color (R, G, B) and an opacity level (opacity) are set for the signal value of each pixel, based on the signal value (a CT value if the image is a CT image) at each voxel position in the three-dimensional image of the extracted structure. In such a case, color templates, in each of which a color and an opacity level are set according to a region of interest, are preliminarily prepared, and a desired color template is selected depending on regions. This enables a region of interest to be visualized in a volume rendering image (VR image).
Meanwhile, there are also cases in which arrows that indicate the presence of tumors, text indicating the name of each structure included in three-dimensional images, and the like are added to the position of a corresponding structure as a label. Further, a method in which a spine is extracted and a label is automatically added to the extracted spine, and a method in which a bronchus is extracted and an anatomical medical term is added to the extracted bronchus as a label have been proposed.
A method in which when displaying each of the three-dimensional images, to which labels are added in such a manner as described above, text described in each label is displayed by pointing to a position where the label is added has been proposed (refer to Patent Document 1 (PCT Japanese Publication No. 2010-500089)). In this method, the text includes the name of a segmented anatomical structure, descriptions thereof, or abnormality thereof. Further, a method in which while a doctor makes an observation by using three-dimensional images and examines a subject by utilizing an endoscope, a label on which the doctor's observation is described is displayed on an endoscopic image being displayed in the case that the endoscope approaches the position to which the observation is added has been proposed (refer to Patent Document 2 (Japanese Unexamined Patent Publication No. 2011-206168)).